There are many instances when a shaft has a marginal length which is sealingly received in a reciprocatory manner within a seal means. The end of the shaft is often threaded, and must be extended through the seal means. Sometime it is necessary that the threaded marginal end of the shaft have the same diameter or almost the same diameter as the medial part of the shaft which is sealingly received within the seal means. Great care must be taken in extending the threaded end of the shaft through the seal means, or otherwise, the seal means will become damaged at the most critical part thereof, thereby necessitating the replacement of the seal means, or alternatively, causing early failure of the seal. The labor involved in replacing some seal means is enormous in both time and cost.
In order to overcome this undesirable seal damage, those skilled in the art have determined that damage to the seal can be avoided by placing several layers of tape about the threads of the shaft end, and thereafter forcing the shaft through the seal means and relying upon the tape to insulate the seal surface from the threaded surface. This is not always an acceptable procedure for the reason that often the working area precludes satisfactory removal of the tape from the shaft threads. Moreover, the adhesive and pieces of the tape are liable to become imbedded within the threaded surface, which sometimes interferes with the proper assembly of the threaded shaft end.
Others sometime have a special female plug fabricated, so that the plug can be screwed onto the threads, thereby protecting the seal interior from the threaded shaft end as it is telescoped through the seal. This procedure is undesirable because the inaccessibility of the shaft end makes removal of the protector therefrom difficult. Moreover, the cost of fabricating the threaded protector is sometime considerable. Furthermore, the thread protector sometime must be built with extremely thin sidewalls in order to accommodate both the outside diameter of the threaded surface and the inside diameter of the seal.
Accordingly, it would be desirable to have made available a thread cover which can be magnetically affixed to a threaded shaft end with the cover having means thereon for isolating the threaded shaft surface from the inner surface of the seal means. Apparatus which achieves this desirable goal is the subject of the present invention.